Degreeing in 40/80 cam shafts

[ORFORD2004]

I'm not Guy Croft but that's the way I did it:

I don't see the need for timing marks on the pulley. For timing my cams i have to find the lobe center of the cam and be shure that the crank was at 110 degrees. you need a dial indicator and a degree Wheel for that job.

The way i did it is you find the real TDC. The way to do it is to use the infamous screwdriver method to find TDC.
Then you install your degree wheel on the flywheel and put a piece of wire attach to the engine to 0 degree.

Next is to put the dial indicator in the plug hole. Not much of steel in that area for my magnetic base so i made a steel bracket that use the valve cover bolts to hold steady. So you install your dial indicator and you have some pressure on the dial. Set to 0 and turn the crank clockwwise. When you read let's say .002, note the number on the degree Wheel. Continue turning and when you are .002 before the 0 you set, note the number on the degree Wheel. For example if you read 355 and 3. You have to move your pointer 1 degree up to 4 so the reading will be 356 and 4. Equal from the zero. From now the pointer or the degree wheel can't move. Retest to be shure. Now you have your true TDC.

Now you have to find the lobe center of the cam. For that you have to install the dial indicator 90 degrees from the valve tappet and clear the lobe rotation. The trick i found, sorry for the purist was to use electric tape and a piece of steel wire at the end of my dial indicator because my needle was to big to fit on the side of the cam and clearing the lobe. When there is full pressure to the tappet, you install your dial indicator with some pressure on it. Set to 0 and turn the crank clockwise. when the valve start closing let's say .002, note the number on the degree Wheel. Continue turning and when the valve is .002 before the 0 you set, note the number on the degree Wheel. For example if you read 84 and 134, you take 134-84=50/2=25. So 25+84=109. Your lobe center is at 109 degree and you want 110. If you move to 85 you will read 135 also. So 135-85=50/2=25. So 85+25=110. So you set your degree wheel to 85 degree and using the adjustable pulley turn back the dial indicator to .002 when the crank is at 85 degree. Retest and you should read 85 and 135. Now your lobe center is at 110 degree.
Same thing for the other side.

[Nut124]

I have reused flywheel bolts before. I use locktite w flywheel and cam, aux shaft bolts.

As long as flywheel bolts develop torque evenly and consistently, I'm happy. Make sure the steel washer plate is there, under the bolt heads.

Con rod bolts are what worries me. They are often over torqued and stretched.

I tried ARP head bolts studs but did not like them. They are extremely rigid. Torque development is not gradual but very quick, sharp. Over torque starts snapping nut threads before stretching the stud. They may require some experience to use correctly, like.

[Nut124]

I'm not Guy Croft but that's the way I did it:

I don't see the need for timing marks on the pulley. For timing my cams i have to find the lobe center of the cam and be shure that the crank was at 110 degrees. you need a dial indicator and a degree Wheel for that job.

The way i did it is you find the real TDC. The way to do it is to use the infamous screwdriver method to find TDC.
Then you install your degree wheel on the flywheel and put a piece of wire attach to the engine to 0 degree.

Next is to put the dial indicator in the plug hole. Not much of steel in that area for my magnetic base so i made a steel bracket that use the valve cover bolts to hold steady. So you install your dial indicator and you have some pressure on the dial. Set to 0 and turn the crank clockwwise. When you read let's say .002, note the number on the degree Wheel. Continue turning and when you are .002 before the 0 you set, note the number on the degree Wheel. For example if you read 355 and 3. You have to move your pointer 1 degree up to 4 so the reading will be 356 and 4. Equal from the zero. From now the pointer or the degree wheel can't move. Retest to be shure. Now you have your true TDC.

Now you have to find the lobe center of the cam. For that you have to install the dial indicator 90 degrees from the valve tappet and clear the lobe rotation. The trick i found, sorry for the purist was to use electric tape and a piece of steel wire at the end of my dial indicator because my needle was to big to fit on the side of the cam and clearing the lobe. When there is full pressure to the tappet, you install your dial indicator with some pressure on it. Set to 0 and turn the crank clockwise. when the valve start closing let's say .002, note the number on the degree Wheel. Continue turning and when the valve is .002 before the 0 you set, note the number on the degree Wheel. For example if you read 84 and 134, you take 134-84=50/2=25. So 25+84=109. Your lobe center is at 109 degree and you want 110. If you move to 85 you will read 135 also. So 135-85=50/2=25. So 85+25=110. So you set your degree wheel to 85 degree and using the adjustable pulley turn back the dial indicator to .002 when the crank is at 85 degree. Retest and you should read 85 and 135. Now your lobe center is at 110 degree.
Same thing for the other side.

I'm no Guy Croft either.

I think your method is fine if you just want to check the C/L of a known cam as installed. It does make some assumptions about the symmetricity of the open/close profiles. Is there a reason why you could not measure 0.050", 0.100", 0.150" angles at both opening and closing to determine C/L?

For understanding the effect of a cam on performance, it is important to somewhat precisely know the valve open close events timing. This you do not gain if just checking for top lift angle.



I like to fully profile a new cam in a spare head to get accurate profile.

[jon8christine]

This is from the kelfordcams website... Makes sense but I don't have any personal experience.

The Incorrect Method / Myths About the Centerline

Never use the ‘centerline' method that zeros somewhere near full lift and then splits the difference between two readings on the degree wheel either side etc, this is not accurate.

The full lift position is not relevant to the engine it is only a quick reference figure used in dialogue amongst engine builders. Incoming intake charge or outgoing exhaust does not care where the centerline is, they only respond to filling or evacuating the cylinder based on relevant valve opening and closing events.

It is not accurate to use the centerline number to determine valve events.

It is accurate to use the valve event figures to determine a centerline number.

The problem with the centerline method is it has you finding the theoretical point of peak lift in relation to crank rotation. This method makes the assumption that the lobe or valve motion you are checking is symmetrical; with its opening side being the exact same shape as the closing side of the lobe. Most modern cam lobes are asymmetrical, with the opening side of the lobe being much more aggressive and the closing side being gentler. Therefore when you attempt to locate the middle (or centerline) of the asymmetrical lobe there is an automatic error. It could be as little as 2° or as much as 6° depending on the actual lobe design. Also, the centerline method does not really indicate if your camshaft was properly produced, as no confirmation of the duration at any given point. Our method will verify correct valve opening and closing and duration.

[ORFORD2004]

Is there a reason why you could not measure 0.050", 0.100", 0.150" angles at both opening and closing to determine C/L?

No, as long as you use the same number both side of the cam.